<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
      .dialog {
          position: relative;
          margin-top: 50px;
          margin-left: 50px;
          padding-left: 20px;
          padding-right: 20px;
          width: 300px;
          line-height: 2;
          background: transparent;
          /* background-color: lightblue; */
          border: 1px solid red;
          color: #fff;
      }

      .dialog::after {
          content: '';
          position: absolute;
          border: 8px solid;
          border-color: transparent lightblue transparent transparent;

      }
  </style>
</head>
<body>
    <div class="dialog">这是一个对话框鸭！</div>
</body>
</html>
